Extension vs Conservatory Cost UK
Decide extension vs conservatory in 60 seconds — and avoid the £30k 'conservatory I can't use in winter' mistake.
Estimates based on UK trade benchmark data, updated 2 May 2026. Methodology →
Extensions and conservatories can both add space, but they deliver very different comfort levels and long-term value. This guide compares extension vs conservatory costs in the UK in 2026, including realistic budget bands, usability trade-offs, and where each option makes the most sense.
Most projects fall between £28,560 and £38,640. Budget refreshes start near £9,120; premium projects reach up to £81,900.
Two ways to take action on Extension vs Conservatory costs
Pick the path that fits where you are — running early numbers, or pressure-testing a quote you've already got.
Typical UK Cost by Scenario
Typical timeline: 2 to 14 weeksBudget
£18,000
typical figure
- Focused essentials
- Practical finishes
Mid-range
Most common£33,600
typical figure
- Balanced specification with core upgrades
- Reliable materials
Premium
£61,110
typical figure
- Premium materials
- Wider scope with higher coordination demands
Figures are typical UK averages including labour, materials, and VAT at 20% for standard-rated work.
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Typical UK Cost Ranges for Extension vs Conservatory
| Item | Cost Range |
|---|---|
| Conservatory (lean-to, small) | £9,600 – £18,000 |
| Conservatory (medium) | £14,400 – £26,400 |
| Orangery / solid roof conservatory | £24,000 – £54,000 |
| Single-storey extension (15 m²) | £26,400 – £54,000 |
| Single-storey extension (25 m²) | £42,000 – £78,000 |
| Year-round comfort | £0 – £0 |
All prices are approximate UK averages including labour, materials, and VAT at 20% (2026). Some qualifying renovations for empty homes may use the reduced 5% VAT rate.
Mini Extension vs Conservatory cost calculator
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Real UK Cost Examples
- Budget scenario (3-bed terrace, Cardiff): focused essentials and practical finishes. Not done: major layout or structural changes. Approx cost: £7,600 to £22,400.
- Mid-range scenario (typical homeowner, 4-bed detached): balanced specification with core upgrades and reliable materials. Approx cost: £23,800 to £32,200.
- High-end scenario (bungalow): premium materials and wider scope with higher coordination demands. Main cost drivers: specification level and complexity. Approx cost: £33,600 to £68,250.
Related next steps:
What You Can Get For Your Budget
- Around £19,600: core refresh and essential upgrades, usually with no major layout change.
- Around £28,000: balanced refit scope with better materials and targeted performance improvements.
- £42,000+: wider flexibility on finish quality, scope depth, and more complex works.
Hidden Costs to Watch For
- Groundworks and thermal-spec upgrades can push costs beyond entry-level assumptions.
- Waste removal, making-good, and repeat trade visits are common late-budget increases.
- Compliance and certification items are often missing from initial summary quotes.
- In most UK projects, scope changes after works start are where costs escalate fastest.
Related next steps:
Should You Do This Renovation?
- Usually worth it when extension vs conservatory solves a clear usability, compliance, or energy-performance problem.
- Less worth it when the main issue is cosmetic and resale timing is short-term.
- ROI is strongest when scope is disciplined and specification matches local value levels.
Common Cost Mistakes
- Underestimating labour and preliminaries while focusing only on material prices.
- Changing scope mid-project without budget re-baselining.
- Choosing the cheapest quote without checking detailed inclusions and exclusions.
- Running too little contingency for hidden defects and compliance upgrades.
Key Cost Factors
- Conservatory — cheaper per m²; often permitted development; can be cold in winter and hot in summer unless upgraded; uPVC or aluminium frame.
- Extension — full insulation, heating, and building regs; usable year-round; higher cost; may need planning for larger sizes.
- Orangery / solid roof — bridges the gap; more comfortable than all-glass conservatory but usually cheaper than full extension.
- Planning — conservatories often permitted dev; extensions beyond certain size need planning.
- Use — if you want a proper room (e.g. kitchen-diner), extension is the right choice; if you want a sunroom or occasional space, conservatory can suffice.
- Location — both cost 15–25% more in London and the South East.
Cost Checkpoints
Use these checkpoints to sequence spend decisions, protect your core scope, and reduce late-stage budget overruns.
- Prioritise single-storey extension (25 m²) first: typical range £42k to £78k can shift the whole project budget if scope changes late.
- Prioritise orangery / solid roof conservatory next: typical range £24k to £54k can shift the whole project budget if scope changes late.
- Use £28k as a working midpoint and hold a contingency of roughly 10% to 15% for unknowns and making-good works.
- Request like-for-like quotes with labour, materials, and exclusions split out so you can compare options without hidden scope gaps.
5 line items every fair Extension vs Conservatory quote should include
Use this checklist to spot missing scope before you sign — each item names what should be priced and what to ask for if it isn't.
- 1
Cost comparison — conservatory vs extension per m²
Conservatory: £800-£1,500/m² (basic poly roof to glass); £1,500-£2,200/m² (solid/tiled roof). Extension: £2,400-£3,500/m² (single-storey, full Building Regs, year-round usable). Extension is typically 2-3x more expensive per m² for similar floor area — but produces a fundamentally different result.
Fair UK range: Conservatory £8k-£25k typical; Extension £30k-£60k for similar floor area.
Ask: What's the per-m² rate, and what's the year-round usability of each option?
- 2
Year-round usability — the deciding factor
Polycarbonate-roof conservatories: unusable in summer (overheats to 40°C+) and winter (cold, condensation). Glass-roof conservatories: better but still 5-10°C colder than house in winter. Solid/tiled conservatory: usable year-round but starts approaching extension cost. Extension: full Building Regs Part L = year-round comfortable.
Fair UK range: Polycarbonate conservatory: usable ~6 months/year. Extension: usable 12 months/year (true habitable space).
Ask: Will I genuinely use this space in January? Polycarbonate conservatories rarely deliver on year-round use claims.
- 3
Building Regs treatment
Conservatories EXEMPT from Building Regs IF: floor area ≤30m², separated from house by external-quality door, no fixed heating system independent of house. If you want heating or solid roof, Building Regs apply (typically £400-£800). Extensions ALWAYS need Building Regs — that's why they're properly habitable.
Fair UK range: Conservatory: Building Regs exempt if rules followed. Extension: full Building Regs always (£400-£1,200).
Ask: Will the conservatory keep the dividing door for Building Regs exemption, or do I want true integration (which triggers Part L)?
- 4
Resale value uplift comparison
Polycarbonate conservatory: often £0 value uplift, sometimes -£5k (buyers see it as repair liability). Glass conservatory: £3k-£10k uplift typical. Solid-roof conservatory: £15k-£30k uplift (functions as extra room). Extension: £30k-£60k uplift typical, often best ROI of any UK home improvement.
Fair UK range: Conservatory ROI: poor to negative. Solid-roof conservatory: 50-80% ROI. Extension: 60-100% ROI.
Ask: Get 2-3 estate agent valuations comparing post-build value under each scenario. Conservatory ROI is often disappointing.
- 5
Planning permission likelihood
Conservatories: usually permitted development (no planning needed) if rear, single-storey, within size limits. Extensions: often need planning if over 3m/4m rear extension limits. Conservation areas restrict both.
Fair UK range: Conservatory: 90% permitted development. Extension: 50% permitted development depending on size.
Ask: Does each option fall within Permitted Development limits, or does either need full planning?
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7 red flags that mean you might be overcharged on a Extension vs Conservatory quote
UK-specific signals — each red flag explains why it matters and the question that surfaces the truth.
Conservatory salesperson promising 'year-round use' with polycarbonate roof
Why it matters: Polycarbonate roofs make conservatories unusable in summer (overheating) and winter (cold + condensation). Anyone promising 'year-round use' with polycarbonate is misleading you. For year-round use, you need solid/tiled roof — which approaches extension cost.
Ask: If I want year-round use, what roof type and heating do you recommend? Polycarbonate isn't suitable.
High-pressure sales tactics from national chain conservatory firms
Why it matters: Anglian, Everest, Britelite, SafeStyle have all faced regulatory action over inflated initial prices and 'today only' discounts. Their actual product is usually fine but you'll pay 50-100% more than equivalent local installer rates.
Ask: Can I take 2 weeks to compare quotes? National chain salespeople punish you for taking time — that's the answer.
Extension quote without considering conservatory alternative
Why it matters: If your goal is occasional/seasonal use of garden space, an extension is over-engineered (and 2-3x more expensive). A contractor who doesn't even discuss conservatory option for that use case is biased.
Ask: Could the same use case be met by a quality conservatory at lower cost?
Conservatory quote that removes dividing door without Building Regs
Why it matters: Removing the dividing door between house and conservatory makes it part of the heated house — triggers Building Regs Part L. Most polycarbonate/glass conservatories fail Part L. Removing the door without compliance work is illegal.
Ask: Will the dividing door stay (for Building Regs exemption), or are you doing the Part L work to make this part of the heated house?
Conservatory quote without DGCOS or HIES membership
Why it matters: DGCOS (Double Glazing & Conservatory Ombudsman Scheme) and HIES provide insurance-backed guarantees. Conservatory installers fail at higher-than-average rates. Without IBG, the warranty dies with the installer.
Ask: Are you a member of DGCOS or HIES? Is the warranty insurance-backed?
Extension quote significantly below £2,000/m² (outside London)
Why it matters: UK 2026 typical for single-storey extension is £2,400-£3,500/m². Below £2,000/m² usually means: missing professional fees, Party Wall Awards, structural engineer, Part L insulation, or quality finishes.
Ask: How are you achieving this extension price? What's included for structural fees, Party Wall, and finishes?
Both quotes ignore long-term running cost
Why it matters: Polycarbonate conservatory used as 'occasional' room: minimal running cost. Glass conservatory used year-round (with electric heaters): £400-£800/year electricity. Extension to Part L: £100-£200/year heating. Over 10 years, the running cost gap can be £4-£8k — partially offsetting build cost difference.
Ask: What's the realistic annual running cost for each option, and how does it shift the lifetime cost comparison?
Spot a couple of these on your Extension vs Conservatory quote? Upload it for a full red-flag scan and fair-rate comparison.
How to negotiate a Extension vs Conservatory quote
A simple framework, a verbatim script you can paste into an email or text, and the topic-specific levers that move the price.
Framework
- 1Be honest about intended use FIRST. If you want occasional/seasonal garden room, conservatory is fine. If you want year-round habitable space, extension is the right answer despite higher cost.
- 2Get THREE quotes — for whichever direction you commit to. For conservatory, AVOID national chains (Anglian/Everest/Britelite) on first compare; get local DGCOS-registered installer quotes first.
- 3Demand both options costed if you're genuinely undecided. Reputable contractors who do both will give honest comparison; salespeople for one type won't.
- 4Get 2-3 estate agent valuations. Conservatory ROI is often poor to negative; extension ROI is often best of any improvement. The market verdict often makes the decision clearer than functional considerations.
Verbatim script
I'm comparing a conservatory to a single-storey extension. My intended use is [year-round habitable / summer-only garden room]. Could you quote for the [conservatory option / extension option] honestly, and tell me what scope I'd need from the alternative type for a like-for-like comparison? I want to compare: build cost, year-round usability, running cost, value uplift, and disruption.
Topic-specific levers
- Use-driven decision: occasional/summer use = conservatory (cost-effective for the use case). Year-round habitable = extension (don't try to make a conservatory work year-round; it won't).
- Roof upgrade: solid/tiled conservatory roof costs £3-£8k more than polycarbonate but transforms year-round usability — and if going solid, you might as well build a proper extension for not much more.
- Local installer for conservatory: avoid Anglian/Everest/Britelite for first quotes (often 50-100% above local installer rates for same product). Get a local DGCOS-registered installer quote first.
- Planning route: conservatory usually permitted development; extension often needs planning. If timing matters, conservatory delivers in 8-12 weeks vs extension's 20+ weeks.
- Long-term ROI: extension typically adds £30-£60k value (60-100% ROI on cost). Conservatory adds £0-£15k (0-50% ROI). For investment-driven thinking, extension wins despite higher cost.
Want to know which line items on your Extension vs Conservatory quote are above market before you negotiate? Upload it for a fair-rate comparison.
10 questions to ask before hiring a extension contractor or conservatory installer
Vet on competence, insurance, paperwork and process — not price alone. Each question spells out the answer you want and why.
1. Have you completed BOTH conservatories AND extensions, or are you a specialist in one?
Why it matters: Single-type specialists will bias the recommendation. Builders who do both honestly can give comparative advice.
2. Can you provide cost + value estimates for BOTH options with this property?
Why it matters: Reputable contractors give both options. Single-option quotes mean you're not getting independent comparison.
3. If conservatory: are you a member of DGCOS or HIES?
Why it matters: DGCOS/HIES provides ombudsman + insurance-backed warranties. Conservatory installers fail at higher rates — IBG matters.
4. If extension: are you a member of FMB, TrustMark, or NHBC?
Why it matters: FMB/TrustMark vet contractors on workmanship and finances. Extension is £30-£60k+ project — IBG warranty essential.
5. What's the realistic year-round usability of the conservatory option you're proposing?
Why it matters: Most conservatories are unusable December-February (cold/condensation) and July-August (overheating). Reputable installers are honest; salespeople aren't.
6. What's your warranty, and is it insurance-backed for whichever option you're proposing?
Why it matters: Industry norm: 10-year IBG for extension structural; conservatory IBG via DGCOS scheme. Verbal-only warranties worthless.
7. Will the conservatory keep the dividing door (Building Regs exempt), or do I want full integration (triggers Part L)?
Why it matters: Removing dividing door is a one-way decision triggering significant Building Regs work. Make this decision deliberately.
8. Have you got local estate agent contacts who can value the post-build property under each scenario?
Why it matters: Conservatory ROI is often disappointing. Local market verdict matters more than glossy brochures.
9. What's the realistic running cost (heating) for each option?
Why it matters: Conservatory used year-round: £400-£800/year heating. Extension to Part L: £100-£200/year. Over 10 years, the running cost gap is significant.
10. What's your payment schedule, and what's the deposit?
Why it matters: Industry norm: 10-25% deposit. Conservatory salespeople often demand large upfront (50%+) — that's a red flag.
Already chosen a extension contractor or conservatory installer and got a quote? Run it through our Quote Checker before you commit.
Typical Timeline
| Item | Duration |
|---|---|
| Conservatory (small) | 2 to 3 weeks |
| Conservatory (medium) or orangery | 3 to 6 weeks |
| Single-storey extension | 8 to 14 weeks |
Regional Cost Variations
Extensions and conservatories in London and the South East cost 15–25% more than national averages.
Costs in your area
Compare regional benchmarks for extension vs conservatory using the same UK baseline assumptions.
Ways to Reduce Costs
- If budget is tight and you accept seasonal use, a conservatory is the cheaper option.
- For a kitchen or daily living space, an extension is worth the extra cost for comfort.
- Orangery or solid-roof conservatory improves comfort over all-glass; compare cost to a small extension.
- Check permitted development limits for both; conservatories have size and height rules.
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Frequently Asked Questions
Extension vs Conservatory: Decision Guide
| Item | Cost Range |
|---|---|
| Typical cost range | £55k-£140k – £8k-£35k |
| Best for | Year-round integrated living space – Lower-cost additional daylight room |
| Thermal performance | Higher with compliant insulation standards – Varies significantly by glazing specification |
| Longevity/value | Usually stronger resale impact – Lower capital risk but lower perceived value uplift |
Extension Pros
- Creates permanent, fully integrated floor area.
- Better year-round comfort and energy performance when designed well.
- Often stronger long-term value for family homes.
Extension Cons
- Higher cost and longer programme.
- More planning/building-control complexity.
- Greater disruption to existing living areas.
Conservatory Pros
- Lower upfront budget and faster installation.
- Good option for light-filled informal space.
- Can be attractive when major structural work is not viable.
Conservatory Cons
- Comfort can drop in winter/summer without premium spec.
- Generally lower resale impact than a true extension.
- Layout integration is often weaker than masonry builds.
When each option works best
- Retired couple selects high-spec conservatory for bright garden room at lower cost than a full extension.
- Young family chooses extension to create insulated kitchen-dining hub used all year and better aligned with resale goals.
When to Choose Each Option
- Choose extension when thermal comfort, integrated layout, and long-term value are your priorities.
- Choose conservatory when budget speed and natural light are the main drivers, and occasional-season use is acceptable.
- For borderline cases, compare lifecycle costs including heating/cooling rather than headline install price alone.